The process according to the present invention is of the type described in the Compagnic Plastic Omnium Patent French Patent No. 2,218,987 and comprises the stages of winding a tape of fluoro resin onto a mandrel, particularly of raw PTFE, obtained such as by lubricated extrusion and calendering, winding of the tape in a plurality of layer, heating the tape thus wound onto the mandrel to a temperature above the gelling temperature of the fluoro resin for a sufficient time to cause gelling, cooling the tube and the mandrel and withdrawing the mandrel situated inside the tube.
In the prior document the winding of the turns onto the mandrel is carried out so that the axis of the tape forms an angle of between approximately 45.degree. and 90.degree. with the axis of the tube, the successive windings being preferably carried out with turns of opposite direction so as to alternate the inclinations of the layers of tape to the axis of the tube.
While being satisfactory from the viewpoint of mechanical strength, nevertheless, with some chemical products which are conveyed, the tubes formed in this way exhibit a disadvantage related to phenomena of diffusion through the wall of the tube as a result of interstices which remain along the edges of the wound tape at crossovers between the layers wound at different winding angles.
The present invention proposes to provide a process for the manufacture of tubes made of fluoro resin, especially of polytetrafluoroethylene, which constitutes an improvement to the process described previously by avoiding the abovementioned disadvantages.